\textbf{Single phase growth of materials with high polar mismatch at the interface}

Growing thin films on polar surfaces has always been a challenge. An even greater challenge though, has been growing thin films on polar surfaces with polar mismatch at the interface. The divergence of surface free energy inhibits appearance of a sharp interface in these materials. Here for the first time, we report successful growth of LaNiO$_{3}$ on SrTiO$_{3}$ in (111) direction with correct phase. We show that by controlling the substrate's electronic and stoichiometric properties along with careful tune of thermodynamic parameters during the growth, it is possible to grow a single phase thin film of LaNiO$_{3}$. Using RHEED, LEED, STM and TEM, we show that the interface is sharp and there is no structural discontinuity, and the surface of the film preserves its symmetry during the growth. In addition, angle-resolved core-level photoelectron spectroscopy confirms the single phase growth.